Television pick-up tubes



Dec. 6, 1955 R. THElLE 2,726,351

TELEVISION PICK-UP TUBES Filed July 16, 1955 LINE FRAME SCAN SCAN GENERATOR GENERATOR H.F-SOURCE AMPUFIER SLIDE FLYING SPOT SCANNER Inventor fikvfa n! 7221/:

Attorneys ;tube and more between adjacentlines] v I A h I V .ning line, the cross-section of thebeam at themid-point I bra n andth .t ec rodeateachfsuc e, f l

is nni gir ster-l puency which is .highin relation to the amplitude of oscillation;of the be tude of the oscillations'being, varied along.

United States Patent 2,726,351 TELEVISION PrqK- r r nes Richard Theile, Marburg Lahn), Germany, assignor to Pye Limit d, C mbridg E g nd, a British company sh pre ent i ven relat t te ev o p pa t cu arlvto ni kp tubes w t hi .vel dt s ann u a i l ?,.kn n a sx asw e an im geif noscbpe In these types oflpick up tubes thcangle .of incidence b ween the sc nnin eam rornrth gun nd th target electrode changes as the beam moves acrossthe target electrode, whichmeans that the current density of the exploring electron beam varies across the serrate, of the target electrode due tochangesin, the cross-sectional area of theibeam impinging thereon.

This change inlcrossmectioi alarea of the beam where it i mping es onlth e target lproduces gaps varying siie F r: n ta c ,i y. 93 g sca of thelinewillfb smaller than lat either end ofthe line the targetele'ctr'ode at a more oblique angle. 'Thus any .onejlinewill tend to be Mrrower in the centrethanf at eitherend,giving' rise to t elinejs. .Thes e gaps will further vary in width n a frame direction due t he .cha'ns jo curr n d nsity an v aq s iel i ts the scanning of "a co jl ete. raster'. as IflbcYefe plaine d, pro uce pur u i IS de sit e ove "the s riaceofth jarge l ctt' j he .pr n in entio ha f r hjej t to. provid an rra emen ft red igp fla mdm lth ffhors'es b eiiect. t A

co t o aflsn st qftt ec n en iq rth eleetrqn gun 1s caused to produce an eetron he miforr'ninj'g 'a manner to at'least partially comp shoe effect. 7

According to another aspect of the invention, .theelectronjbeam is adapted to form a spohpn'ithe target surface of the pick-up tube, which spot 'is small 'compar'edwith {the line pitch, and the electron beam is oscillated in 'a direction transverse to "the line ,diijectionat a frequency which is highin relation to'th'e linefr'equency, the amplith n' t of each line and'i'n successive lines of each'frame or raster in .sucha rnanner thatthe width. of each individual line and of the lines eachfframdorraster remains substantially constant.

The amplitude, of the high,.fr'equency oscillations applied to the, spot can hemvariedqby; modulating a l-iigh frequency. oscillation applied, tothe ,.elc ctron beam :Twith .line.,-and frame deflecting 2 frequency which oscillates the spot in such a manner that the spot amplitude yaries in a manner to maintain the line width substantially constant. Thus, if the spot is of smallest size at the middle of a scanning line, the gap between that line and an adjacent line, would normally be greatest at this point, and therefore, according to the invention, the component of the modulation waveform derived from theline deflecting waveform generator is arranged to increase the amplitude of oscillation of the spotbyl greatest amount at this point in each line. Similarly the component of the modulation waveform derived from the deflecting waveform generator' at frame frequency is superimposed on the higher frequency in such a manner that the spot is oscillated with increased amplitude by this component of the moduin relation to the other lines of the raster in thezframe direction.

Preferably, the waveforms derived from the line and frame deflecting Waveform generators are combined with the source of high frequency signals which oscillates the electron ,beam so as to produce modulated oscillations which may be applied to the electron beam in any suitable manner.

However, the mod ulation waveform which is required accurately to compensate for the horseshoe effects pro duced on the target electrode is of 'a complex nature, and the present invention further provides an arrangement wherein the waveform for varying the amplitude of the high frequency oscillation applied to the spot is derived "from a copy' of the pattern of the horseshoe effect prov electrode of the pick-up tube. Since the'pattern'of the horseshoe efiect produced on any one tube remains substantially unaltered, a geometrical reproduction of the pattern ca'n be easily made. i According to a furtherfeature of the invention, therefore, a geometrical reproduction of the charge pattei n producing the horseshoe'eifect on a pick-up tube is traversed by a scanning bearnof which the line and frame defleeting waveforms are in synchroniSm with theline and frame deflecting waveformsof the pick-up tube, so as to t on the tube. The geometrical 3 bet, for example, by drawing drawing, "in which:

the invention and V produce a signal modulated according to theip'attern of the horseshoe effect, which signal is applied to vary the amplitude of oscillation 'of'a wave havinga frequency which is high in relation to the line, frequency, said: oscih lations, being appliedto oscillate the electron beam in a 'direction transverse tofthe line direction and thereby substantially compensate for the horseshoe efiect produced reproduction of the horseshoe effect pattern' may be produced on an opaque memor photography and incorporated in a monoscope or similar picture signal gen erator tube. 1 i V In order that the invention may be more fully understood, reference will now be made to the accompanying Figure lis a diagram of onearrangement according to ;Figure 2 shows a horseshoe eifect pattern.

In the arrangement of Figure 1, a copy of the horseshoe effect pattern shown in Figure 2, is formed on a slide 1 which is positioned in front of a flying-spot scanner 2, the

light W i9 Pfi$ th l .d ,.fi n o a Ph electric "cell fs l'preferably a cell incorporating an electron multipler. The line andfrarne deflecting wavefor rnsgfor the fiying-sp'otscanner and the deflecting waveforms for the pick-up tube are preferably derived from the same -g'ener'ators 4 and 5 so asto bein correct time relationship. -The'0utput voltage from the multiplier cell 3, varies'ac- ,cordingvtothe intensity of the light'beam passingthrough ath slide-1 and thus:produces a voltage varying' in accordance with the pattern of the horseshoe effect. In this way a modulation waveform is produced which can be used to compensate for the horseshoe effect of a particular tube. This modulation waveform is fed through an amplifier 6, and combined with the high frequency oscillations generated at 7, to produce a modulated high frequency signal which may be applied to modulate the electron beam of the pick-up tube 8 in any suitable manner. Advantageously, a separate coil 9 may be disposed on the neck of the pickup tube, adjacent the line and frame deflector coils 10, the moduated high frequency being fed to this additional coil to modulate the electron beam in the frame direction.

The high frequency oscillations are preferably at least twice the highest modulation frequency component of the video signal, and for a high definition system may be of the order of megacycles per second.

I claim:

1. Arrangement for reducing the effect of spurious signals such as the horseshoe effect," in television pick-up tubes with high velocity scanning, comprising means for forming the electron beam of the pick-up tube into a spot on the target surface of the pick-up tube, which spot is small compared with the pitch of the scanning lines of the pick-up tube, means for producing high frequency oscillations at a frequency which is high in relation to the line frequency, means for producing a modulation waveform, means for applying said modulation waveform to vary the amplitude of the high frequency oscillations along the length of a line scan, and means for applying said high frequency oscillations to modulate the electron beam of said pick-up tube in a direction transverse to the line direction.

2. Arrangement for reducing the effect of spurious signals such as the horseshoe effect, in television pickup tubes with high velocity scanning, comprising means for forming the electron beam of the pick-up tube into a spot on the target surface of the'pick-up tube, which spot is small compared with the pitch of the scanning lines' of the pick-up tube, means for producing high frequency oscillations at a frequency which is high in relation to the line frequency, line and frame deflecting waveform generators, means for producing a modulation waveform from the line and frame deflecting waveform generators,

means for applying said modulation to vary the amplitude of the high frequency oscillations along the length of a line scan and in successive lines of'each frame and. means for applying said high frequency oscillations to modulate the electron beam of said pick-up tube in a direction transverse to the line direction.

3. Arrangement for reducing the effect of spurious signals such as horseshoe effect, in television pick-up tubes with high velocity scanning, comprising means for forming the electron beams of the pick-up tube into a spot on the target surface of the pick-up tube, which spot is small compared with the pitch of the scanning lines of the pick-up tube, means for producing high frequency oscillations at a frequency which is high in relation to the line I frequency, means for producing a modulation waveform from a geometrical reproduction of the pattern of the horseshoe effect produced on the target electrode of the pick-up tube, means for applying said modulation to vary the amplitude of the high frequency oscillations along the length of a line scan, and means for applying said high frequency oscillations to modulate the electron beam of said pick-up tube in a direction transverse to the-line direction.

4. Arrangement as claimed in claim 3 wherein the geometrical reproduction of the horseshoe effect pattern is produced on an opaque'member incorporated in a picture signal generator tube.

5. Arrangement as claimed in claim 3, wherein the geometrical reproduction of the horseshoe effect pattern is produced on a slide positioned in front of a flying spot scanner, the light passing through the slide falling upon a photo-electric cell, the output voltage of which is combined with the source of high frequency oscillations before it is applied to the pick-up tube.

6. Arrangement for reducing the effect of spurious signals such as the horseshoe effect in television pick-up tubes with high velocity scanning, comprising means for producing a geometrical reproduction of the charge pattern producing the horseshoe effect," means for generating high frequency oscillations, means for producing a modulation waveform according to the pattern of the horseshoe effect from said geometrical reproduction, means for feeding the modulation waveform to vary the amplitude of the high frequency oscillationand means for applying said modulated high frequency oscillations to said pick-up tube to oscillate the electron beam in said pick-up tube in a direction transverse to the line direction.

7 Arrangement for reducing the effect of spurious signals such as the horseshoe efiect in television pickup tubes with high velocity scanning, comprising means for producing a geometrical reproduction of the charge pattern producing the horseshoe effect, means for generating line and frame'deflection waveforms, means for deflecting the electron beam in said pick-up tube from said line and frame deflection waveforms, means for generating high frequency oscillation, a scanning beam controlled by said line and frame deflection waveforms scanning said geometrical reproduction of the horseshoe effect to produce a modulation Waveform, means for feeding the modulation waveform to vary the amplitude of the high frequency oscillation generator and means for applying said modulated high frequency oscillations to signals such as the horseshoe effect" in television pick-up tubes with high velocity scanning, comprising means for producing a geometrical reproduction of the charge pat-, tern producing the horseshoe effect, means for generating line and frame deflection waveforms, means for deflecting the electron beam in said pick-up tube from said line and frame deflection waveforms, means for generating high frequency oscillation of at least twice the highest frequency modulation component of'the video signal produced by the pick-up tube, a scanning beam controlled by said line and frame deflection waveforms scanning said geometrical reproduction of the horseshoe effect to produce a modulation waveform, means for feeding the modulation waveform to vary the amplitude of the high frequency oscillation generator and'means for applying said modulated high frequency oscillations to a coil disposed on the neck of said pick-up tube to oscillate the electron beam in said pick-up tube in a direction transverse to the line direction. I

9. Arrangement as claimed in claim 7, wherein the geometrical reproduction of the horseshoe effect pat- References Cited in the file of this patent UNITED STATES PATENTS 2,093,157 Nakashima et al Sept. 14, 1937 2,269,226 Rohats Jan. 6, 1942 2,270,232 Rosenthal Jan. 20, 1942 2,339,833 Bedford Jan. 25, 1944 2,578,343 Ekvall Dec. 11, 1951 2,582,014 De France et a1 Jan. 8, 1952 

